1. Field of the Invention
The present invention generally relates to a variable valve timing mechanism for an internal combustion engine. More specifically, the present invention relates to a variable valve timing mechanism in which appropriate lift characteristics are attained for engine start-up.
2. Background Information
Variable valve timing mechanisms are used in internal combustion engines for opening and closing an intake valve or an exhaust valve that is linked to a crankshaft of the internal combustion engine and for varying the lift characteristics of the intake valve or the exhaust valve according to the rotation of a control shaft.
One example of such a variable valve timing mechanism is disclosed in Japanese Laid-Open Patent Publication No. 2005-226543. In this publication, the variable valve timing mechanism is provided with a stopper mechanism for mechanically regulating the upper and lower limit positions of the allowed range of rotation of the control shaft. A target control value of the control shaft is set within a range that is smaller than the range of rotation allowed by the stopper mechanism. Basically, the stopper mechanism of Japanese Laid-Open Patent Publication No. 2005-226543 has a minimum operational-angle stopper, a maximum operational-angle stopper and a stopper pin. The minimum and maximum operational-angle stoppers extend along the axial direction of the control shaft from an actuator plate towards the control shaft. The minimum and maximum operational-angle stoppers are affixed to a cylinder head. The stopper pin that is fixed to the control shaft and extends along the radial direction of control shaft.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved variable valve timing mechanism. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.